The present invention relates to an improved audible signal to provide audible alarms in a wide variety of devices including, for example, automobiles and trucks, industrial equipment, medical devices, traffic signals, appliances and the like. Such devices can use a piezoelectric transducer and associated circuitry to produce sound at a given frequency. The transducer flexes in response to an applied voltage. If an oscillating voltage is applied to the transducer at an appropriate rate, the flexing of the transducer produces an audible sound of substantial volume. As the wide variety of potential uses shown above suggests, these audible signals need to be able to operate in a wide variety of conditions and environments. One problem facing such audible signals is water corrosion. Audible signals have always had a problem with liquids being able to gather in the front of the housing. Once the front of the audible signal housing fills with liquid, it is only a matter of time before the transducer corrodes and failures occur. In addition, the audible signal cannot emit a sound if there is an accumulation of liquid sitting on the transducer. Currently, audible alarms containing a piezoelectric transducers must be turned upside down to protect them from buildups of liquid in the front of the housing.
What is needed is an audible signal which includes a barrier against liquids, while at the same time generating a signal that is not dampened in decibel level by the barrier.
In the invention, the audible signal is sealed by a hydrophobic material, such as polytetrafluoroethylene (PTFE). Typically, a disc of such material can be suitably attached to the audible signal by means of a hot melt, sonic weld, silicone adhesive, or similar fastening means. Such a hydrophobic material will result in an audible signal which is at least water resistant, while not materially affecting the decibel level or tone of the audible signal.